1. Field of the Invention
The invention relates to a single-handle, sanitary mixing valve having control elements composed of at least two discs, one of which serves as a fixed valve seat disc with two inlet openings for cold and hot water, while the second disc, movably disposed on the valve seat disc, has a control edge that at least partially reduces the free flow area for cold water at the inlet opening when the movable disc is shifted to its central position by the operating handle, as compared to the corresponding free flow area of the hot water inlet opening of the fixed valve seat, in the mixed water temperature ranges conventionally bounding a so-called comfort zone.
2. Description of the Prior Art
When mixing fittings are operated in combination with thermally or hydraulically controlled flow heaters, malfunctions will often occur in the ordinary mixed water temperatures because the heaters require certain minimum flow rates. If these minimum flow rates are not maintained, the heaters will switch off in whole or in part.
To avoid such malfunctions, there are known single-handle mixing valves of the type described in which the mixing chamber opening in the movable disc is asymmetrically shaped relative to a symmetrical port configuration in the fixed valve seat disc, to ensure that the free flow area at the inlet opening for cold water will be smaller than on the corresponding hot water side in the mixed water temperature ranges. Such a mixing valve, from which the present invention departs, is disclosed in German Letter of Disclosure No. 3,310,080. It has proved successful in practice. .A disadvantage of the known devices is that the movable disc, owing to the special configuration of the mixing chamber opening, must be a special part, that is, differing from the corresponding discs of conventional single-handle mixing valves.